Pre-stressed rolling mills which maintain maximum loading on the working rolls are provided with load transfer blocks having hydraulic motors for acting against the pre-stress loading to obtain the desired loading on the working rolls for a particular rolling operation.
More uniform rolling results are obtained if the load transfer blocks are incompressible, or as nearly so as possible, so that any movement of the rolls that would produce a gap larger than the transfer blocks provide for will subject the rolls to the full pre-stress force and thus prevent variations in the thickness of the sheet.
If a sheet breaks or the end of a sheet or strip quickly moves beyond the rolls so that the material being rolled no longer takes any of the pre-stress of the mill, the transfer blocks are subject to violent shock loading as the full pre-stress force of the mill comes upon them. In order to prevent such shock, this invention provides substantially incompressible transfer blocks with shock absorbers that come into action when the load rises above a certain predetermined force. This shock absorbing action is obtained by having a compressible gas which holds the shock-absorbing section of the transfer block rigid during normal operation; and which absorbs the shock when a workpiece moves beyond the pass between the working rolls.
The preferred embodiment of the invention provides a hydraulic motor, with a minimum of oil in it to make the block substantially incompressible, and a second motor subject to gas pressure and exerting a force that yields when the transfer block is subjected to excessive pressure.
One feature of the preferred embodiment is that gas pressure acts against a larger area so that it can hold the hydraulic motor in position, even though the hydraulic pressure is greater than the gas pressure.
Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.